When a node reaches its low watermarks and wakes up kswapd, notify all userspace programs waiting on the workingset page age histogram of the memory pressure, so a userspace agent can read the workingset report in time and make policy decisions, such as logging, oom-killing, or migration.
Sysfs interface: /sys/devices/system/node/nodeX/workingset_report/report_threshold time in milliseconds that specifies how often the userspace agent can be notified for node memory pressure.
Signed-off-by: Yuanchu Xie yuanchu@google.com --- include/linux/workingset_report.h | 4 +++ mm/internal.h | 6 +++++ mm/vmscan.c | 44 +++++++++++++++++++++++++++++++ mm/workingset_report.c | 39 +++++++++++++++++++++++++++ 4 files changed, 93 insertions(+)
diff --git a/include/linux/workingset_report.h b/include/linux/workingset_report.h index 23d2ae747a31..589d240d6251 100644 --- a/include/linux/workingset_report.h +++ b/include/linux/workingset_report.h @@ -35,7 +35,11 @@ struct wsr_page_age_histo { };
struct wsr_state { + unsigned long report_threshold; unsigned long refresh_interval; + + struct kernfs_node *page_age_sys_file; + /* breakdown of workingset by page age */ struct mutex page_age_lock; struct wsr_page_age_histo *page_age; diff --git a/mm/internal.h b/mm/internal.h index 151f09c6983e..36480c7ac0dd 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -209,8 +209,14 @@ extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason /* * in mm/wsr.c */ +void notify_workingset(struct mem_cgroup *memcg, struct pglist_data *pgdat); /* Requires wsr->page_age_lock held */ void wsr_refresh_scan(struct lruvec *lruvec, unsigned long refresh_interval); +#else +static inline void notify_workingset(struct mem_cgroup *memcg, + struct pglist_data *pgdat) +{ +} #endif
/* diff --git a/mm/vmscan.c b/mm/vmscan.c index 5f04a04f5261..c6acd5265b3f 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2535,6 +2535,15 @@ static bool can_age_anon_pages(struct pglist_data *pgdat, return can_demote(pgdat->node_id, sc); }
+#ifdef CONFIG_WORKINGSET_REPORT +static void try_to_report_workingset(struct pglist_data *pgdat, struct scan_control *sc); +#else +static inline void try_to_report_workingset(struct pglist_data *pgdat, + struct scan_control *sc) +{ +} +#endif + #ifdef CONFIG_LRU_GEN
#ifdef CONFIG_LRU_GEN_ENABLED @@ -3936,6 +3945,8 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) if (!min_ttl || sc->order || sc->priority == DEF_PRIORITY) return;
+ try_to_report_workingset(pgdat, sc); + memcg = mem_cgroup_iter(NULL, NULL, NULL); do { struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); @@ -5650,6 +5661,36 @@ void wsr_refresh_scan(struct lruvec *lruvec, unsigned long refresh_interval) } } } + +static void try_to_report_workingset(struct pglist_data *pgdat, + struct scan_control *sc) +{ + struct mem_cgroup *memcg = sc->target_mem_cgroup; + struct wsr_state *wsr = &mem_cgroup_lruvec(memcg, pgdat)->wsr; + unsigned long threshold = READ_ONCE(wsr->report_threshold); + + if (sc->priority == DEF_PRIORITY) + return; + + if (!threshold) + return; + + if (!mutex_trylock(&wsr->page_age_lock)) + return; + + if (!wsr->page_age) { + mutex_unlock(&wsr->page_age_lock); + return; + } + + if (time_is_after_jiffies(wsr->page_age->timestamp + threshold)) { + mutex_unlock(&wsr->page_age_lock); + return; + } + + mutex_unlock(&wsr->page_age_lock); + notify_workingset(memcg, pgdat); +} #endif /* CONFIG_WORKINGSET_REPORT */
#else /* !CONFIG_LRU_GEN */ @@ -6177,6 +6218,9 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) if (zone->zone_pgdat == last_pgdat) continue; last_pgdat = zone->zone_pgdat; + + if (!sc->proactive) + try_to_report_workingset(zone->zone_pgdat, sc); shrink_node(zone->zone_pgdat, sc); }
diff --git a/mm/workingset_report.c b/mm/workingset_report.c index 370e7d355604..3ed3b0e8f8ad 100644 --- a/mm/workingset_report.c +++ b/mm/workingset_report.c @@ -269,6 +269,33 @@ static struct wsr_state *kobj_to_wsr(struct kobject *kobj) return &mem_cgroup_lruvec(NULL, kobj_to_pgdat(kobj))->wsr; }
+static ssize_t report_threshold_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + struct wsr_state *wsr = kobj_to_wsr(kobj); + unsigned int threshold = READ_ONCE(wsr->report_threshold); + + return sysfs_emit(buf, "%u\n", jiffies_to_msecs(threshold)); +} + +static ssize_t report_threshold_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t len) +{ + unsigned int threshold; + struct wsr_state *wsr = kobj_to_wsr(kobj); + + if (kstrtouint(buf, 0, &threshold)) + return -EINVAL; + + WRITE_ONCE(wsr->report_threshold, msecs_to_jiffies(threshold)); + + return len; +} + +static struct kobj_attribute report_threshold_attr = + __ATTR_RW(report_threshold); + static ssize_t refresh_interval_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { @@ -412,6 +439,7 @@ static ssize_t page_age_show(struct kobject *kobj, struct kobj_attribute *attr, static struct kobj_attribute page_age_attr = __ATTR_RO(page_age);
static struct attribute *workingset_report_attrs[] = { + &report_threshold_attr.attr, &refresh_interval_attr.attr, &page_age_intervals_attr.attr, &page_age_attr.attr, @@ -437,6 +465,9 @@ void wsr_register_node(struct node *node) pr_warn("WSR failed to created group"); return; } + + wsr->page_age_sys_file = + kernfs_walk_and_get(kobj->sd, "workingset_report/page_age"); } EXPORT_SYMBOL_GPL(wsr_register_node);
@@ -450,6 +481,14 @@ void wsr_unregister_node(struct node *node)
wsr = kobj_to_wsr(kobj); sysfs_remove_group(kobj, &workingset_report_attr_group); + kernfs_put(wsr->page_age_sys_file); wsr_destroy(mem_cgroup_lruvec(NULL, kobj_to_pgdat(kobj))); } EXPORT_SYMBOL_GPL(wsr_unregister_node); + +void notify_workingset(struct mem_cgroup *memcg, struct pglist_data *pgdat) +{ + struct wsr_state *wsr = &mem_cgroup_lruvec(memcg, pgdat)->wsr; + + kernfs_notify(wsr->page_age_sys_file); +}